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Abstract

A set of fully automated algorithms that is specialized for analyzing a three-dimensional optical coherence tomography (OCT) volume of human skin is reported. The algorithm set first determines the skin surface of the OCT volume, and a depth-oriented algorithm provides the mean epidermal thickness, distribution map of the epidermis, and a segmented volume of the epidermis. Subsequently, an en face shadowgram is produced by an algorithm to visualize the infundibula in the skin with high contrast. The population and occupation ratio of the infundibula are provided by a histogram-based thresholding algorithm and a distance mapping algorithm. En face OCT slices at constant depths from the sample surface are extracted, and the histogram-based thresholding algorithm is again applied to these slices, yielding a three-dimensional segmented volume of the infundibula. The dermal attenuation coefficient is also calculated from the OCT volume in order to evaluate the skin texture. The algorithm set examines swept-source OCT volumes of the skins of several volunteers, and the results show the high stability, portability and reproducibilityof the algorithm.

Figures (13)

Fig. 1. A schematic of the SS-OCT system (left) and an example of the OCT volume of forehead skin in vivo (right). In the schematic, HSL is the high-speed wavelength scanning light source; C, the circulator; RM, the reference mirror; OL, the objective; and BR, the balanced photo-receiver.

Fig. 3. A realigned B-scan (left) and the corresponding OCT volume (right). All the A-scans are realigned to flatten the sample surface. The green line and the green box indicate the flatten sample surface.

Fig. 5. (a) The distribution of epidermal thickness (epidermal thickness map), and (b) the detected surface and dermal-epidermal junction in a B-scan, where the red curve indicates the surface of the skin, and the blue curve indicates the dermal-epidermal junction.

Fig. 6. (a) An example of a B-scan. The red curve indicates the detected surface and the red area indicates the domain of integration. (b) An example of the en face shadowgram; white corresponds to low signal intensity and black corresponds to high signal intensity. The white spots indicate the infundibula. (c) The histogram of the shadowgram (b). Pixel intensities are normalized by the mean and standard deviation of the histogram. The distributions under the red line (10% of the maximum) were not considered while calculating the mean and standard deviation. (d) A binary map of the distribution of the infundibula. (e) The red circles indicate the island spots detected as circles by the Danielsson distance mapping algorithm. The circles are superimposed on the shadowgram (b).

Fig. 7. (a) A B-scan of the original OCT volume and that of the segmented OCT volume. The white arrows and the green spots indicate the infundibula. (b) Corresponding shadow-gram. Click the figure (a) to see a movie (2.4 MB).

Fig. 8. (a) The original OCT volume, (b) a segmented OCT volume, and (c) the top view of the segmented OCT volume. The blue, green, and orange volumes in the right figure correspond to the segments of the epidermis, infundibula, and the remaining volume, respectively. In (c), the infundibula are superimposed on the epidermis. (d) A stereogram of (b) for three-dimensional understanding of the structure. (e) A sebum absorbent tape image. The white spots represent the absorbed sebum. Click the figure (b) to see a movie (1.9 MB).

Table 3. The mean epidermal thicknesses, populations and occupation ratios of the in-fundibula, and dermal attenuation coefficients of a single subject. The measurements were repeated ten times, and the unbiased standard deviations of each parameter are also shown.

Metrics

Table 1.

The mean epidermal thicknesses, populations and occupation ratios of the in-fundibula, and dermal attenuation coefficients of the five subjects.

Mean epidermal
thickness (μm)

Infundibulum
population
(cm-2)

Infundibulum
occupation ratio
(%)

Dermal attenuation
coefficient
(cm-1)

Subject 1

100 ± 28

225

20.9

31.7

Subject 2

90 ± 8

194

19.9

20.5

Subject 3

100 ± 3

181

21.6

24.8

Subject 4

100 ± 29

181

20.3

27.5

Subject 5

90 ± 10

188

22.4

31.9

Mean

98

194

21.0

27.3

Table 2.

The mean epidermal thicknesses (MET), the infundibulum populations (IP) and infundibulum occupation ratios (OP) of the five subjects.

MET (μm)

IP (cm-2)

OP (%)

MET (μm)

IP (cm-2)

OP (%)

Forearm

Cheek

Subject 1

70 ± 20

25

3.9

100 ± 30

369

33.8

Subject 2

63 ± 5

81

8.9

60 ± 23

435

35.1

Subject 3

65 ± 5

38

7.9

60 ± 30

462

35.6

Subject 4

96 ± 4

31

4.8

90 ± 20

344

34.3

Subject 5

76 ± 6

44

6.1

70 ± 20

462

35.6

Mean

72

44

6.3

76

412

34.7

Table 3.

The mean epidermal thicknesses, populations and occupation ratios of the in-fundibula, and dermal attenuation coefficients of a single subject. The measurements were repeated ten times, and the unbiased standard deviations of each parameter are also shown.

Mean epidermal
thickness (μm)

Infundibulum
population
(cm-2)

Infundibulum
occupation ratio
(%)

Dermal attenuation
coefficient
(cm-1)

Forehead

98.3 ± 5.7%

239 ± 15.6%

19.7±3.2%

34.4 ± 5.3%

Forearm

67.6 ± 4.1%

49 ± 30.4%

7.5 ± 13.3%

51.6 ± 5.2%

Cheek

66.8 ± 5.8%

372 ± 9.8%

34.4 ± 1.8%

45.2 ± 7.9%

Tables (3)

Table 1.

The mean epidermal thicknesses, populations and occupation ratios of the in-fundibula, and dermal attenuation coefficients of the five subjects.

Mean epidermal
thickness (μm)

Infundibulum
population
(cm-2)

Infundibulum
occupation ratio
(%)

Dermal attenuation
coefficient
(cm-1)

Subject 1

100 ± 28

225

20.9

31.7

Subject 2

90 ± 8

194

19.9

20.5

Subject 3

100 ± 3

181

21.6

24.8

Subject 4

100 ± 29

181

20.3

27.5

Subject 5

90 ± 10

188

22.4

31.9

Mean

98

194

21.0

27.3

Table 2.

The mean epidermal thicknesses (MET), the infundibulum populations (IP) and infundibulum occupation ratios (OP) of the five subjects.

MET (μm)

IP (cm-2)

OP (%)

MET (μm)

IP (cm-2)

OP (%)

Forearm

Cheek

Subject 1

70 ± 20

25

3.9

100 ± 30

369

33.8

Subject 2

63 ± 5

81

8.9

60 ± 23

435

35.1

Subject 3

65 ± 5

38

7.9

60 ± 30

462

35.6

Subject 4

96 ± 4

31

4.8

90 ± 20

344

34.3

Subject 5

76 ± 6

44

6.1

70 ± 20

462

35.6

Mean

72

44

6.3

76

412

34.7

Table 3.

The mean epidermal thicknesses, populations and occupation ratios of the in-fundibula, and dermal attenuation coefficients of a single subject. The measurements were repeated ten times, and the unbiased standard deviations of each parameter are also shown.